Equivalent test method for detecting dynamic and thermal stability of grounding material

Abstract

The invention provides an equivalent test method for detecting dynamic and thermal stability of a grounding material. The equivalent test method comprises the following steps: constructing a temperature field simulation model; determining a short-time withstand current value Imax, calculating a temperature rise T0 according to simulation software, adjusting environmental parameters, respectively applying forward and reverse power frequency currents Imin, the amplitudes of which are obviously smaller than Imax, to two ends of the grounding conductor to determine an equivalent current and an equivalent time, and finally carrying out an actual test to verify the dynamic thermal stability. The temperature field simulation model comprising the frame body and the grounding conductor is constructed through the temperature field simulation software, the heating effect of the grounding conductor is subjected to simulation calculation, the action time required for the grounding conductor to reach the same temperature under the action of different currents is determined, and the grounding conductor is subjected to simulation calculation. A long-time and small-amplitude power frequency current is adopted to perform equivalence on a short-time and large-amplitude power frequency short-circuit current, so that the capacity of test equipment is greatly reduced, the miniaturization of detection equipment is realized, and the test detection efficiency of a grounding material is improved.

Description

Technical Field

[0001] The present invention relates to the field of high voltage technology, and in particular to an equivalent test method for detecting the dynamic thermal stability of grounding materials. Background Art

[0002] The grounding system is an integral component of the power grid. A concealed, underground facility, it serves as the sole means for lightning strikes and short-circuit fault currents to enter the ground, making it the cornerstone of the safe operation of power systems. The reliability of grounding materials is a crucial prerequisite for the safety and effectiveness of the entire grounding system. With the development of ultra-high voltage (UHV) and smart grids, grid capacity has increased dramatically, placing increasingly stringent demands on the safe operation of grounding networks and the performance requirements for grounding materials. For grounding projects, in addition to ensuring that the overall electrical characteristic parameters of the grounding device are met, the dynamic thermal stability of the grounding conductor material itself when subjected to power-frequency short-circuit fault currents is also a critical factor affecting the safety and service life of the grounding system.

[0003] Due to the high ground short-circuit fault currents in power systems, in order to assess whether the grounding material meets the requirements for dynamic thermal stability under short-circuit fault currents, it is usually necessary to apply a power frequency current of tens of kiloamperes to the material for testing. This requires large and bulky testing equipment, making the testing process extremely inconvenient and requiring only laboratory testing, making it impossible to conduct on-site random inspections and acceptance. In actual projects, significant quality discrepancies exist between the samples sent by some manufacturers to testing units for laboratory testing and the products actually delivered on-site. The phenomenon of "not matching the specifications" is a common occurrence. Due to the lack of effective technical supervision methods for rapid on-site testing, construction management units can only accept the main quality issues that arise in the actual application of new grounding materials based on laboratory test reports or even visual appearance alone. This is highly arbitrary, making it difficult to eliminate inferior products during construction, and thus creating numerous safety hazards for subsequent equipment operation. Summary of the Invention

[0004] In view of this, the present invention proposes an equivalent test method for detecting the dynamic thermal stability of grounding materials, aiming to solve the problems in the prior art that a large test current is required to assess the dynamic thermal stability of grounding materials under short-circuit fault current, the test process is inconvenient and on-site inspection and acceptance cannot be carried out.

[0005] The present invention proposes an equivalent test method for detecting the dynamic thermal stability of grounding materials, comprising:

[0006] Constructing a temperature field simulation model including a frame and a grounding conductor, wherein the grounding conductor is arranged horizontally within the frame, and setting physical parameters of the frame and the grounding conductor according to parameters of the soil environment in which the grounding conductor is actually buried;

[0007] Determine the dynamic thermal stability short-time withstand current value I of the grounding conductor according to its relevant properties max , and in the temperature field simulation model, an amplitude of I is applied to one end of the ground conductor max A positive power frequency current is applied to the other end with an amplitude of I max The reverse power frequency current is used to perform coupled calculation of the current field and the temperature field, and obtain the temperature rise T0 of the grounding conductor after the current lasts for a period of time t;

[0008] In the temperature field simulation model, the physical parameters of the frame are adjusted to the parameters corresponding to the air environment, the physical parameters of the ground conductor are kept unchanged, and a temperature with an amplitude significantly smaller than I is applied to one end of the ground conductor. max Forward power frequency current I min , apply an amplitude of I to the other end min The reverse power frequency current is used to perform coupling calculation of the current field and the temperature field to obtain the temperature rise curve of the grounding conductor, and the time t0 required for the grounding conductor temperature rise value to reach T0 is determined based on the above, and t0 is greater than t; I min and t0 are the equivalent test current and equivalent test time of the dynamic thermal stability of the grounding conductor respectively;

[0009] Obtain a ground conductor sample with the same specifications as the above ground conductor, place it in the air, measure its initial DC resistance R0, and apply a power frequency test circuit with an amplitude of I to the ground conductor sample. min An axial current is applied for a duration of t0. After the grounding conductor sample cools to room temperature, its DC resistance R1 is measured again. The deviation between R1 and R0 is used to determine whether the dynamic thermal stability of the grounding conductor meets the requirements.

[0010] Furthermore, in the above-mentioned equivalent test method for detecting the dynamic thermal stability of the grounding material, the short-time withstand current value I of the grounding conductor is calculated according to the following formula: max :

[0011]

[0012] Where S is the cross-sectional area of the grounding conductor; t is the duration of the short-time withstand current of the grounding conductor, which is 1s; and C is the dynamic thermal stability coefficient of the grounding conductor.

[0013] Furthermore, in the above-mentioned equivalent test method for detecting the dynamic thermal stability of the grounding material, each dimension of the frame is at least 10 times the corresponding dimension of the grounding conductor.

[0014] Furthermore, in the above-mentioned equivalent test method for detecting the dynamic thermal stability of the grounding material, the physical parameters of the frame include: resistivity, thermal conductivity and specific heat capacity.

[0015] Furthermore, in the above-mentioned equivalent test method for detecting the dynamic thermal stability of grounding materials, the physical parameters of the grounding conductor include: resistivity, density and specific heat capacity.

[0016] Furthermore, in the above-mentioned equivalent test method for detecting the dynamic thermal stability of grounding materials, the frame is in the shape of a cube, a truncated cone, a rectangular parallelepiped or a cylinder.

[0017] Furthermore, in the above-mentioned equivalent test method for detecting the dynamic thermal stability of grounding materials, if the deviation between R1 and R0 is less than or equal to 20%, it is determined that the grounding conductor meets the dynamic thermal stability requirements; otherwise, it is determined that the grounding conductor does not meet the dynamic thermal stability requirements and is an unqualified product.

[0018] Furthermore, in the above-mentioned equivalent test method for detecting the dynamic thermal stability of grounding materials, COMSOL finite element software is used to construct a temperature field simulation model including a frame and a grounding conductor, and coupled calculations of the current field and temperature field are performed under different set working conditions.

[0019] Furthermore, in the above-mentioned equivalent test method for detecting the dynamic thermal stability of grounding materials, the power frequency test circuit includes: an AC test power supply, a current measuring device, a control switch and a voltage measuring device; wherein,

[0020] The current measuring device is connected in series to the output end of the AC test power supply; the voltage measuring device is connected in parallel to both ends of the grounding conductor sample; and the control switch is provided between the output end of the current measuring device and the grounding conductor sample.

[0021] Furthermore, in the above-mentioned equivalent test method for detecting the dynamic thermal stability of grounding materials, a direct resistance meter is also provided in the power frequency test circuit.

[0022] The equivalent test method for detecting the dynamic thermal stability of grounding materials in the present invention constructs a temperature field simulation model including a frame and a grounding conductor through temperature field simulation software, simulates and calculates the heating effect of the grounding conductor, determines the action time required for the grounding conductor to reach the same temperature under the action of different currents, and uses a long-term, small-amplitude power frequency current to be equivalent to a short-term, large-amplitude power frequency short-circuit current, thereby greatly reducing the capacity of the test equipment, realizing the miniaturization of the detection equipment, increasing the portability of the detection equipment, and improving the test and detection efficiency of the grounding material. At the same time, it supports on-site arrival detection of the grounding material, which is beneficial to improving the construction quality of the power transmission and transformation grounding project and ensuring the safe operation of the power grid. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiment below. The accompanying drawings are for illustration purposes only and are not to be considered as limiting the present invention. The same reference symbols are used throughout the drawings to represent the same components. In the drawings:

[0024] Figure 1 A schematic flow chart of an equivalent test method for detecting the dynamic thermal stability of grounding materials provided in an embodiment of the present invention;

[0025] Figure 2 Schematic diagram of a temperature field simulation model of a grounding conductor material according to an embodiment of the present invention;

[0026] Figure 3 This is a temperature rise curve diagram of the grounding conductor material in an embodiment of the present invention;

[0027] Figure 4 Schematic diagram of test wiring in an embodiment of the present invention. DETAILED DESCRIPTION

[0028] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art. It should be noted that, unless there is a conflict, the embodiments of the present disclosure and the features described in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0029] See Figure 1 and Figure 2 The equivalent test method for detecting the dynamic thermal stability of grounding materials according to an embodiment of the present invention includes:

[0030] Step S1, constructing a temperature field simulation model including a frame 1 and a grounding conductor 2, wherein the grounding conductor 2 is arranged in the frame 1 along the horizontal direction, and the physical parameters of the frame 1 and the grounding conductor 2 are set according to the parameters of the soil environment in which the grounding conductor 2 is actually buried.

[0031] Specifically, the frame 1 is in the shape of a cube, a truncated cone, a rectangular parallelepiped, or a cylinder. Each dimension of the frame 1 is at least 10 times the corresponding dimension of the ground conductor 2. In this embodiment, a cube is selected as the frame 1. For example, a cube of 50m×50m×50m can be selected. The ground conductor 2 is in the shape of a rod, 1m long, and 0.8m from the top surface of the cube.

[0032] The physical parameters of the frame 1 include resistivity, density, thermal conductivity and specific heat capacity.

[0033] The physical parameters of the ground conductor 2 include resistivity, thermal conductivity, density and specific heat capacity.

[0034] Step S2: Determine the dynamic thermal stability short-time withstand current value I of the ground conductor 2 according to the relevant properties of the ground conductor 2. max , and in the temperature field simulation model, an amplitude of I is applied to one end of the ground conductor 2 max A positive power frequency current is applied to the other end with an amplitude of I max The reverse power frequency current is used to perform coupling calculation of the current field and the temperature field, and obtain the temperature rise T0 of the grounding conductor 2 after the current continues for a time t.

[0035] Specifically, a voltage with an amplitude of I is applied to one end of the ground conductor 2. max The power frequency current is applied at the other end with the same amplitude of I max , but the power frequency current in the opposite direction causes the current to form a closed loop in the grounding conductor 2.

[0036] The short-time withstand current value I of the ground conductor 2 is calculated according to the following formula: max :

[0037]

[0038] Wherein, S is the cross-sectional area of the grounding conductor 2; t is the duration of the short-time withstand current of the grounding conductor 2, which is 1s; and C is the dynamic thermal stability coefficient of the grounding conductor 2.

[0039] I max It is determined by the specifications of the grounding conductor 2 material itself, and is generally tens of kA.

[0040] Step S3, in the temperature field simulation model, the physical parameters of the frame 1 are adjusted to the parameters corresponding to the air environment, the physical parameters of the ground conductor are kept unchanged, and a temperature with an amplitude significantly smaller than 1 is applied to one end of the ground conductor. max Forward power frequency current I min , apply an amplitude of I to the other end min The reverse power frequency current is used to perform coupling calculation of the current field and the temperature field to obtain the temperature rise curve of the grounding conductor (such as Figure 3 ), and accordingly determine the time t0 required for the ground conductor temperature rise value to reach T0, t0 is greater than t; I min and t0 are the equivalent test current and equivalent test time of the dynamic thermal stability of the grounding conductor respectively.

[0041] Specifically, a voltage of I is applied to one end of the ground conductor. minThe power frequency current is applied at the other end with the same amplitude of I min , but the power frequency current in the opposite direction causes the current to form a closed loop in the grounding conductor.

[0042] I min It is determined by the maximum feasible current that can be applied to the grounding conductor. The current value is limited by the maximum output capacity of the test equipment. For example, the maximum current value that the test equipment can output is 1kA, then I min It can be set to 1kA; if the maximum current output of the test equipment is 2kA, then I min It can be set to 2kA. In this embodiment, I min Possible values are 0.5kA, 1kA or 2kA, etc.

[0043] Figure 2 In the example, point A is the beginning of the ground conductor, and point B is the end of the ground conductor. In specific implementation, a voltage with an amplitude of I max or I min The forward power frequency current is applied at B with an amplitude of I max or I min A reverse power frequency current of amplitude I can also be applied at A. max or I min The reverse power frequency current is applied at B with an amplitude of I max or I min Forward power frequency current.

[0044] In this embodiment, COMSOL finite element software is used to construct a temperature field simulation model including the frame 1 and the grounding conductor to simulate and calculate the temperature rise effect of the grounding conductor under different burial environments. The specific steps are as follows:

[0045] Based on the actual dimensions and installation environment of the ground conductor, a 3D simulation model consisting of frame 1 and ground conductor 2 is constructed. Physical parameters such as electrical conductivity, thermal conductivity, and specific heat capacity are set for frame 1 and ground conductor 2, respectively, according to the actual application environment. The frame's physical parameters are adjusted to reflect the characteristics of different installation environments, as well as the physical parameters of the ground conductor itself.

[0046] Apply a power frequency current I of a specific amplitude to both ends of the grounding conductor. min Or short-time withstand current I max, performing coupled calculations of the current and temperature fields, taking into account the Joule heating generated by current flowing through the conductor and the resulting temperature rise. To simulate the heat exchange between the grounding conductor and the surrounding medium, a certain heat exchange coefficient (representing the thermal conductivity between the grounding conductor and the buried environment) is set between the cube and the external medium. This allows for accurate calculation of the grounding conductor's temperature rise due to current flow. This allows for the temperature trend of the grounding conductor to be determined after a period of continuous current flow.

[0047] The temperature rise curve of the grounding conductor obtained by coupling the current field and temperature field using COMSOL finite element software is as follows: Figure 3 As can be seen from the figure, when current is applied to the ground conductor, the temperature of the ground conductor gradually rises over time. However, due to heat conduction and heat exchange in the surrounding medium, the relationship between temperature rise and time is not linear, but rather gradually slows down. By simulating the temperature rise trend curves under high and low currents, we can determine the time equivalence relationship between the two when reaching the same temperature.

[0048] Step S4: obtain a ground conductor sample with the same specifications as the above ground conductor, place it in the air, measure its initial DC resistance R0, and apply a power frequency test circuit with an amplitude of I to the ground conductor sample. min An axial current is applied for a duration of t0. After the grounding conductor sample cools to room temperature, its DC resistance R1 is measured again. The deviation between R1 and R0 is used to determine whether the dynamic thermal stability of the grounding conductor meets the requirements.

[0049] Specifically, if the deviation between R1 and R0 is less than or equal to 20%, it is determined that the grounding conductor meets the dynamic thermal stability requirement; otherwise, it is determined that the grounding conductor does not meet the dynamic thermal stability requirement and is an unqualified product.

[0050] It can be obviously concluded from the above that the equivalent test method for detecting the dynamic thermal stability of grounding materials provided in this embodiment constructs a temperature field simulation model including a frame and a grounding conductor through temperature field simulation software, simulates and calculates the heating effect of the grounding conductor, determines the action time required for the grounding conductor to reach the same temperature under different currents, and uses a long-term, small-amplitude power frequency current to be equivalent to a short-time, large-amplitude power frequency short-circuit current, thereby greatly reducing the capacity of the test equipment, realizing the miniaturization of the detection equipment, increasing the portability of the detection equipment, and improving the test efficiency of the grounding material. At the same time, it supports on-site arrival detection of the grounding material, which is beneficial to improving the construction quality of the power transmission and transformation grounding project and ensuring the safe operation of the power grid.

[0051] See Figure 4In the above embodiment, the power frequency test circuit includes: an AC test power supply 3, a current measuring device 4, a control switch 5 and a voltage measuring device 7; wherein the current measuring device 4 is connected in series to the output end of the AC test power supply 3; the voltage measuring device 7 is connected in parallel to both ends of the grounding conductor sample 6; and the control switch 5 is arranged between the output end of the current measuring device 4 and the grounding conductor sample 6.

[0052] Specifically, the current measuring device 4 is an ammeter, and the voltage measuring device 7 is a voltmeter. The control switch 5 is a relay switch.

[0053] Of course, the power frequency test circuit may also include: a direct resistance meter for collecting the current data of the current measuring device and the voltage data of the voltage measuring device in real time, and calculating the resistance value of the grounding conductor material sample to be tested based on the current data and voltage data.

[0054] In summary, the present invention simulates and calculates the heating effect of the grounding conductor through temperature field simulation software, determines the action time required for the grounding conductor to reach the same temperature under different currents, and uses long-term, small-amplitude power frequency current to be equivalent to short-term, large-amplitude power frequency short-circuit current, thereby greatly reducing the capacity of the test equipment, realizing the miniaturization of the detection equipment, increasing the portability of the detection equipment, and improving the test and detection efficiency of the grounding material. At the same time, it supports on-site arrival detection of the grounding material, which is conducive to improving the construction quality of the power transmission and transformation grounding project and ensuring the safe operation of the power grid.

[0055] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. An equivalent test method for detecting the dynamic thermal stability of grounding materials, characterized in that: include: Constructing a temperature field simulation model including a frame and a grounding conductor, wherein the grounding conductor is arranged horizontally within the frame, and setting physical parameters of the frame and the grounding conductor according to parameters of the soil environment in which the grounding conductor is actually buried; Determine the dynamic thermal stability short-time withstand current value I of the grounding conductor according to its relevant properties max , and in the temperature field simulation model, an amplitude of I is applied to one end of the ground conductor max A positive power frequency current is applied to the other end with an amplitude of I max The reverse power frequency current is used to perform coupled calculation of the current field and the temperature field, and obtain the temperature rise T0 of the grounding conductor after the current lasts for a period of time t; In the temperature field simulation model, the physical parameters of the frame are adjusted to the parameters corresponding to the air environment, the physical parameters of the ground conductor are kept unchanged, and a temperature with an amplitude less than I is applied to one end of the ground conductor. max Forward power frequency current I min , apply an amplitude of I to the other end min The reverse power frequency current is used to perform coupling calculation of the current field and the temperature field to obtain the temperature rise curve of the grounding conductor, and the time t0 required for the grounding conductor temperature rise value to reach T0 is determined based on the above, and t0 is greater than t; I min and t0 are the equivalent test current and equivalent test time of the dynamic thermal stability of the grounding conductor respectively; Obtain a ground conductor sample with the same specifications as the above ground conductor, place it in the air, measure its initial DC resistance R0, and apply a power frequency test circuit with an amplitude of I to the ground conductor sample. min An axial current is applied for a duration of t0. After the grounding conductor sample cools to room temperature, its DC resistance R1 is measured again. The deviation between R1 and R0 is used to determine whether the dynamic thermal stability of the grounding conductor meets the requirements.

2. The equivalent test method for detecting the dynamic thermal stability of grounding materials according to claim 1, characterized in that: The short-time withstand current value I of the grounding conductor is calculated according to the following formula: max : Where S is the cross-sectional area of the grounding conductor; t is the duration of the short-time withstand current of the grounding conductor, which is 1s; and C is the dynamic thermal stability coefficient of the grounding conductor.

3. The equivalent test method for detecting the dynamic thermal stability of grounding materials according to claim 1, characterized in that: Each dimension of the frame is at least 10 times the corresponding dimension of the ground conductor.

4. The equivalent test method for detecting the dynamic thermal stability of grounding materials according to claim 1, characterized in that: The physical parameters of the frame include: resistivity, density, thermal conductivity and specific heat capacity.

5. The equivalent test method for detecting the dynamic thermal stability of grounding materials according to claim 1, characterized in that: The physical parameters of the grounding conductor include resistivity, thermal conductivity, density and specific heat capacity.

6. The equivalent test method for detecting the dynamic thermal stability of grounding materials according to claim 1, characterized in that: The frame is in the shape of a cube, a truncated cone, a rectangular parallelepiped or a cylinder.

7. The equivalent test method for detecting the dynamic thermal stability of grounding materials according to claim 1, characterized in that: If the deviation between R1 and R0 is less than or equal to 20%, it is determined that the grounding conductor meets the dynamic thermal stability requirement; otherwise, it is determined that the grounding conductor does not meet the dynamic thermal stability requirement and is an unqualified product.

8. The equivalent test method for detecting the dynamic thermal stability of grounding materials according to claim 1, characterized in that: COMSOL finite element software is used to construct a temperature field simulation model including the frame and the grounding conductor, and the coupled calculation of the current field and temperature field is performed under different set working conditions.

9. The equivalent test method for detecting the dynamic thermal stability of grounding materials according to claim 1, characterized in that: The power frequency test circuit includes: an AC test power supply, a current measuring device, a control switch and a voltage measuring device; wherein, The current measuring device is connected in series to the output end of the AC test power supply; the voltage measuring device is connected in parallel to both ends of the grounding conductor sample; and the control switch is provided between the output end of the current measuring device and the grounding conductor sample.

10. The equivalent test method for detecting the dynamic thermal stability of grounding materials according to claim 9, characterized in that: The power frequency test circuit is also provided with a direct resistance meter.

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